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Our solar system does not exist in isolation. It formed within a stellar nursery along with hundreds of sibling stars, and even today has the occasional interaction with interstellar objects such as Oumuamua and Borisov. So it\u2019s reasonable to presume that some interstellar material has reached Earth. Recently Avi Loeb and his team earned quite a bit of attention with a study arguing that it had found some of this interstellar stuff on the ocean seabed. But a new study finds that the material has a much more local origin.<\/p>\n
<\/p>\n The original study is based on a 2014 meteor that entered the Earth\u2019s atmosphere off the coast of Papua New Guinea. Observations of its impact trajectory suggested it might have been extraterrestrial in origin. And since we had an idea of where it hit, why not look for its debris? This led Loeb\u2019s team to the seafloor near Papua New Guinea, where they found small, iron-rich spheres known as spherules. The study analyzed the composition of these spherules and found the isotope distribution was so unusual they must have an interstellar origin.<\/p>\n While that sounds compelling, there are a few caveats. The first is that the trajectory of the 2014 meteor isn\u2019t that precisely known. We know the general impact region, but the data simply isn\u2019t good enough to prove that these spherules came from this particular meteor. The second is that \u201cunusual\u201d isotopes aren\u2019t uncommon within our solar system. As the new study shows, there is a distribution of iron isotope ratios for objects originating in the solar system, specifically the ratios of 57<\/sup>Fe and 56<\/sup>Fe. The ratio for the \u201calien\u201d spherules is well within that range. So well that the odds of them being interstellar is less than 1 in 10,000. So these spherules have a local origin.<\/p>\n But they were likely formed from an impact event, so this new study went further. Is there a known impact from which these spherules originated? Turns out there is. The region in which they were found is part of what\u2019s known as the Australasian tektite strewn field. It is a vast field that spans southeast Asia to Antarctica and was caused by a large impact 790,000 years ago. The team looked at other isotope ratios and found they are consistent with other known Australasian tektites.<\/p>\n So these particular spherules have a local origin. But that doesn\u2019t mean interstellar meteorites don\u2019t exist. Given what we know, there are almost certainly interstellar objects on Earth just waiting to be found. We just have to keep looking for them.<\/p>\n Reference:<\/strong> Loeb, A., et al. \u201cRecovery and Classification of Spherules from the Pacific Ocean Site of the CNEOS 2014 January 8 (IM1) Bolide.\u201d Research Notes of the AAS<\/em> 8.1 (2024): 39.<\/p>\n Reference:<\/strong> Desch, Steve. \u201cBe, La, U-rich spherules as microtektites of terrestrial laterites: What goes up must come down.\u201d arXiv preprint<\/em> arXiv:2403.05161 (2024).<\/p>\nLike this:<\/h3>\n